Valves are used in many applications wherein control of flow of a fluid is required or desired. This includes controlling the flow of includes such as oil, fuel, water, gases, etc. Some valves operate to control fluid flow by positioning valving members to control the amount of fluid allowed to pass through the valve. Other valves operate in a switching fashion wherein fluid flow is either turned on or turned off. Such valves may be found in consumer and commercial appliances such as dishwashers, washing machines, refrigerators, beverage vending machines, boilers, etc., whereby water is allowed to flow for a predetermined period of time or until a predetermined volume has been dispensed therethrough. The control of the valve operation may typically be performed by an electronic control circuit, such as a microprocessor based controller, along with its associated drive circuitry, to open and/or close the valving member within the valve.
A problem with such switching valves is the force necessary to open the valving member against the static pressure of the process fluid acting on one side of the valving member. Depending on the application, this pressure may be quite high, particularly when compared with the low pressure on the opposite side of the valving member which, in many appliance applications, is at atmospheric pressure. In addition to the static fluid pressure acting on the valving member tending to keep it closed, many such switching valves also include a spring positioned to apply a force on the valving member. This spring force allows the valve to be closed upon the removal of a drive signal, and maintains a bias force on the valving member to keep it closed.
In such configurations, the valve actuator must overcome both the force generated by the static fluid pressure, which can be quite high and may vary from installation to installation, as well as the spring force, both of which are acting to keep the valve closed. Once these two forces have been overcome, however, the force necessary to continue to open the valve to its fully open position is substantially reduced as the pressure differential across the valving member face drops dramatically. Once this pressure has been equalized, the only remaining force against which the actuator must act is the spring force.
Many electronically controlled switching valves include an electrically actuated solenoid to directly act on a plunger connected to the valving member to move the valving member to its open position. Unfortunately, due to the high pressure differentials that exist for a closed valve and the spring force, the actuator needs to be relatively large so that it is able to reliably operate the valve under all operating conditions and installations. In many industries, such as the consumer appliance industry, strict governmental and certifying agency requirements place a heavy premium on an electric power usage. Further, the appliance industry is highly competitive and the cost of actuators, alone or in addition to the production costs of the valve, provides a significant detriment to developing new technologies and implementing same in the industry.
One example of a prior art instrument for controlling fluid flow is illustrated by FIG. 1. FIG. 1 shows a water supply valve that includes a valve body 10 and an electromagnet unit 20. The valve body 10 includes a water inlet 11, a water outlet 12, and a chamber 14 between the water inlet 11 and the water outlet 12. The water inlet 11 is connected with the chamber 14 via a connecting passage 11a, and a valve seat 13 is provided in the central portion of the chamber 14.
The electromagnet unit 20 drives a first valve 15 to be attached to and detached from the valve seat 13 inside the chamber 14, so that the chamber 14 and the water outlet 12 are connected to and separated from each other. The first valve 15 also partitions the inside of the chamber 14 into the upper and lower sections, such that a pressure chamber 14 is defined in the upper section.
In addition, the first valve 15 includes a diaphragm 15a and a diaphragm holder 15b. The first valve 15 also has a first water passage 17 in the peripheral portion thereof beyond the valve seat 13, and a second water passage 18 in the central portion thereof. The first water passage 17 connects the chamber 14 with a pressure chamber 16, and the second water passage 18 connects the pressure chamber 16 with the water outlet 12.
In the first and second water passages 17 and 18, the second water passage 18 is opened and closed by a second valve 23 on the lower end of a plunger 22 that is installed inside the electromagnet unit 20 under a downward elastic force from a spring 21. Here, the first water passage 17 has an inner diameter smaller than that of the second water passage 18, and controls a flow of supply water following the opening and closing of the second water passage 18.
When power is not supplied to the electromagnet unit 20, the plunger 22 is brought into close contact with the valve seat 13 under its weight and the downward elastic force of the spring 21 and, at the same time, supply water supplied from the water inlet 11 pushes the first valve 15 upward instantaneously in the initial stage. This is because the elastic force of the spring 21, which presses the plunger 22, is smaller than supply water pressure.
However, the first valve 15, which is pushed upward, is directly closed by the supply water pressure. That is, right after water pressure is applied to the underside of the first valve 15, a portion of supply water is introduced into the pressure chamber 16 through the first water passage 17 in the first valve 15. The supply water introduced in this fashion applies a certain pressing force to the upper surface of the first valve 15 to bring the first valve 15 into close contact with the valve seat 13, thereby maintaining a closed circuit state. In this fashion, it is possible to achieve the closed circuit state that stops water supply without consuming electrical power.
In addition, when power is applied to the electromagnet unit 20, the plunger 22 of the electromagnet unit 20 is pushed upward, thereby opening the second water passage 18 of the first valve 15, which was closed by the second valve 23. At this time, the water in the pressure chamber 16 is caused to flow instantaneously toward the water outlet 12 under the atmospheric pressure through the second water passage 18, thereby dropping the pressure inside the pressure chamber 16 to the same as the atmospheric pressure. The force acting on the first valve 15 is released, so that the pressure of water supplied from the water inlet 11 causes the first valve 15 to drop to the upper surface of the valve seat 10. At the same time, a supply water passage passing through the water inlet 11, the chamber 14, and the water outlet 12 of the valve body 10 is maintained in the open circuit state, thereby achieving the intended water supply state.
In order to remove impurities from supply water, which passes through the power-saving electromagnetic water supply valve as described above, a filter 24 is necessarily provided adjacent to the water inlet 11. While the filter 24 prevents the first water passage 17 and the second water passage 18 from being clogged by the cohesion of impurities, these small particles becoming trapped in filter 24 significantly reduce the flow rate compared to an amount of introduced water. In addition, impurities accumulated in the filter increase resistance and thus water is not properly supplied.
Thus, valves such as valve 15 must be carefully engineered and sized to allow proper fluid flow from the inlet into the pressure chamber 16 in order to maintain the valve in a closed condition without requiring power input. This demands careful milling and/or injection molding and construction of the valve and the water passage 17. Moreover, any pollutants in the water source entering the inlet and passing the filter may clog water passage 17. This requires one to either clean or replace the valve in order to provide for keeping the valve in the closed state as blocking water passage 17 prevents equilibrium from establishing between the inlet and pressure chamber 16, instead forcing valve 15 open and causing a leak or further damaging the valve. Moreover, low water pressure could also impact the valve as the ambient pressure may be insufficient to either flow through water passage 17 or insufficient to move valve 15 once the plunger 22 is moved.
Valve construction is further complicated because not only does the static or atmospheric pressure of water systems vary across locations, as well as within a particular location, but pollutant levels also contribute to clogging and/or blocking valving mechanisms, thereby inhibiting their function and requiring frequent service calls to either unblock or replace units that no longer function. This problem is especially prevalent in areas that couple low fluid pressures, such as municipality provided water systems, with high pollutant content of the provided fluid.
What is needed in the art are environmentally friendly, low cost methods for allowing valving mechanisms to function in low pressure situations, especially in low pressure situations where the fluid being controlled contains pollutants.